Intravascular and Intra-atrial Extension of Follicular Thyroid Carcinoma

Dear Editor:

Follicular thyroid carcinoma (FTC) accounts for 10%–27% of thyroid cancers in published series. Microscopic vascular invasion is well recognized in FTC, but massive invasion of tumor into the great veins is rare (1). Only 10 cases of thyroid cancer with invasion into the right atrium have been documented. We report a patient with FTC that invaded not only the great veins but also the right atrium.

An 80-year-old woman presented with dyspnea, cyanosis, orthopnea, and pitting edema. Medical history was significant for a right hemithyroidectomy at age 66 for a 6-cm atypical adenoma. She had been treated with diuretics for chronic heart failure since age 73. Four months before admission, she presented with dyspnea. Diuretics were increased but her symptoms did not improve. She was referred and admitted to our hospital.

Physical examination revealed edema of the face and neck and dilatation of the right jugular vein, suggesting superior vena cava syndrome. There was a surgical scar on the right side of the neck but no palpable tumor there. The electrocardiogram showed atrial fibrillation. Thyroid function tests were normal but serum thyroglobulin was elevated to 16,300 ng/mL (normal, <30 ng/mL). Serum antithyroglobulin antibody levels were 0.8 U/mL (normal range, <0.3 U/mL). Cardiac ultrasound revealed a tumor occupying the right atrium and extending beyond the tricuspid valve (see Supplementary Data, available online at www.liebertonline.com/thy). Enhanced computed tomography (CT) showed that a >17-cm tumor with a cystic component extended from the right internal jugular vein into the superior vena cava and right atrium (see Supplementary Data). There were no masses in the left lobe of the thyroid. Thallium 201 (Tl-201) scintigram revealed concentrations of radioactivity in the same area as the tumor (see Supplementary Data). She was treated with diuretics, cardiac stimulants, and alpha-human atrial natriuretic peptide but there was no symptomatic improvement. She underwent surgical removal of the tumor in the brachiocephalic vein, superior vena cava, and right atrium but not the right internal jugular vein. Pneumonia developed after surgery and she died 2 months later. Histopathological examination of the tumor revealed FTC.

Intra-atrial extension of thyroid cancer is rare as only 10 cases have been reported since 1930 (2 –4). Six were FTC and the others were papillary thyroid carcinoma, atypical thyroid cancer, adenocarcinoma, and undifferentiated cancer. Of the six cases with FTC, two were untreated and died within 2 months and four were treated with tumor thrombectomy. A patient with FTC who had extension of tumor to the heart was reported in 1978 (3). That patient received aggressive surgical therapy with removal of the tumor thrombus from the neck to the right atrium. Of the four cases in the literature treated with tumor thrombectomy, two survived for more than 2 years, suggesting that surgical treatment might prolong survival in some patients. In the present case, the tumor was removed surgically because of uncontrolled heart failure and obstruction of the tricuspid valve but she died 2 months after surgery.

Two types of extension of FTC to the heart have been described (3). One is direct extension through the great veins of the chest, as in the present case. The other is metastatic seeding to other organs. Most patients with direct extension died shortly after their diagnosis as a result of vascular or cardiac involvement. There are only two reports in which FTC with direct vascular invasion appeared to respond to therapy (3,4).

In conclusion, enhanced CT and Tl-201 thyroid scintigraphy is useful for evaluating intra-atrial extension of FTC through the veins. Surgical treatment may ameliorate cardiac failure in a few patients but intra-atrial extension of FTC has a poor short-term prognosis and high mortality rate.